This application claims the benefit of Korean Patent Application No. 2002-17905, filed Apr. 2, 2002, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a duplex printing apparatus, and more particularly, to a duplex printing apparatus with a reduced duplex printing path and a reduced occurrence of a paper jam.
2. Description of the Related Art
FIG. 1 is a cross-sectional view schematically showing a conventional duplex printing apparatus.
Referring to FIG. 1, a pickup roller 11 is rotated to pick up a paper sheet 13 from a stack of paper in a paper cassette 12. The picked up paper sheet 13 is passed through a returning guide 14 and conveyed to a developing unit 15. As the paper sheet 13 is passed through the developing unit 15, an image is developed on the paper sheet 13. Then the paper sheet 13 is passed through a settling unit 16 where the image is settled (fixed) under high temperature and pressure. The paper sheet 13 is then passed through registration rollers 17 to rotate a second returning guide 18 forward. Accordingly, the paper sheet 13 is passed through a discharge roller 19 and discharged out.
During a duplex printing operation, when an end of the paper 13 is passed through the second returning guide 18, a paper sensor (not shown) detects the end of the paper 13. Accordingly, a controller (not shown) rotates the discharge roller 19 in an alternative direction (a forward direction or a reverse direction) a predetermined time after the detection of the end of the paper 13, thereby reversing a conveying direction of the paper 13 before the end of the paper 13 is completely passed through the discharge roller 19. Accordingly, the paper 13 is passed through a rear side of the second returning guide 18 and transferred to a returned paper conveying path 20 that includes the returning roller 21, and then fed back to the returning guide 14 for the duplex printing operation.
In the construction described above, a problem occurs when a paper passing path for the duplex printing operation is relatively long, and when a duplex printing time is lengthened.
Moreover, as the paper passing path is lengthened, components like paper registration rollers and paper guides are additionally required, and the number of the components increases. As a result, the possibility of occurrence of a paper jam also increases.
Furthermore, as the paper passing path is lengthened, a size of the printing apparatus becomes large.
Also, for the duplex printing operation, a user usually purchases another separate duplex printing unit as an option to mount the duplex printing unit at a side of the printing apparatus. This again causes problems of an unnecessarily lengthened paper passing path, in addition to an inconvenience for the user to purchase and mount the separate duplex printing unit.
Accordingly, it is an aspect of the present invention to provide a duplex printing apparatus having an improved structure that has a reduced paper conveying path and requires a simpler structure.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
In order to accomplish the above and/or other aspects of the invention, a duplex printing apparatus according to an embodiment of the present invention includes a developing unit forming an image onto paper being conveyed, a settling unit pressing (fixing) the image on the paper, a discharging roller selectively conveying the paper with the image settled thereon in an alternate direction, a feed frame disposed such that a front side faces the developing unit to guide the conveyance of the paper being picked up, a back plate disposed on a rear side of the feed frame to guide the paper reversed from the discharging unit for the duplex printing operation, a duplex unit guiding the paper, which is passed through the settling unit and reversed from the discharging unit between the rear side of the feed frame and the back plate, and a feeding roller module comprising a feeding roller disposed on a lower portion of the feed frame to convey both the paper fed for a single-side printing operation and the reversed paper for the duplex printing operation toward the developing unit, and a plurality of paper feeding paths for guiding the paper therealong to the feeding roller.
The plurality of paper feeding paths include first and second paper feeding paths for guiding the paper fed from a plurality of built-in paper cassettes to the feeding roller, a third paper feeding path for guiding the paper reversed between the back plate and the feed frame to the feeding roller, and a fourth paper feeding path for guiding the paper fed from an external paper cassette to the feeding roller.
The fourth paper feeding path is formed between the first and the second paper feeding paths and the third paper feeding path.
The feeding roller module further includes a first registration roller unit disposed in contact with the feeding roller to convey the paper fed through the first and the second paper feeding paths, and a second registration roller unit formed between the first and the second paper feeding paths and the fourth paper feeding path to convey the paper fed through the third and the fourth paper feeding paths between the first registration roller unit and the feeding roller.
The first, the second, the third and the fourth paper feeding paths are disposed around the feeding roller and are formed by a plurality of guiding members that are disposed on a side bracket supporting the feed frame.
The feeding roller module includes a main gear coaxially disposed with respect to the feeding roller to rotate the feeding roller, and the main gear and each of a first and second power transmission gears mesh to transmit a power to a reverse feeding registration roller guiding the paper for a duplex driving operation and to a pickup roller picking up the paper from the external paper cassette, respectively.